1. Field of the Invention
The present invention relates to a cyclopentaphenanthrene-based compound and an organic light emitting device employing the same, and more particularly, to an aromatic amine compound including cyclopentaphenanthrene and an organic light emitting device including an organic layer having the same.
2. Description of the Related Art
Organic light emitting devices are active light emitting display devices that emit light by recombination of electrons and holes in a thin layer made of a fluorescent or phosphorescent organic compound (an organic layer) when a current is applied to the organic layer. The organic light emitting devices have advantages such as lightweight, simple constitutional elements, easy fabrication process, superior image quality and wide viewing angle. Furthermore, the organic light emitting devices can accomplish perfect creation of dynamic images and high color purity. The organic light emitting devices also have electrical properties suitable for portable electronic equipment such as low power consumption and low driving voltage.
A multi-layered organic light emitting device using an aluminum quinolinol complex layer and a triphenylamine derivative layer was developed by Eastman Kodak Co. (U.S. Pat. No. 4,885,211), and a wide range of light from ultraviolet lights to infrared lights can be emitted using low-molecular weight materials when an organic emitting layer is formed (U.S. Pat. No. 5,151,629).
Light emitting devices, which are self light emitting display devices, have wide viewing angles, excellent contrast and quick response. Light emitting devices are classified into inorganic light emitting devices using inorganic compounds to form emitting layers and organic light emitting devices (OLED) using organic compounds to form emitting layers. Organic light emitting devices have higher brightness, lower driving voltages and quicker responses than inorganic light emitting devices and can realize multi colors. Thus, organic light emitting devices have been actively studied.
Typically, an organic light emitting device has an anode/organic emitting layer/cathode structure. An organic light emitting device can also have various other structures, such as an anode/hole injection layer/hole transport layer/emitting layer/electron transport layer/electron injection layer/cathode structure or an anode/hole injection layer/hole transport layer/emitting layer/hole blocking layer/electron transport layer/electron injection layer/cathode structure.
Materials that are used in organic light emitting devices can be classified into vacuum deposited materials and solution coated materials according to a method of preparing an organic layer. The vacuum deposited materials may have a vapor pressure of 10−6 torr or greater at the temperature of 500° C. or less and be low molecular materials having a molecular weight of 1200 or less. The solution coated materials may be highly soluble in solvents to be prepared in solution phase, and include aromatic or heterocyclic groups.
When an organic light emitting device is manufactured by vacuum deposition, costs may be increased due to expensive vacuum systems and high resolution pixels may not be easily manufactured if a shadow mask is used to prepare pixels for a natural color display. On the other hand, an organic light emitting device can be easily and inexpensively manufactured using solution coating such as inkjet printing, screen printing and spin coating and can have relatively high resolution compared to when using a shadow mask.
Meanwhile, when an organic light emitting device is operated or stored at a high temperature, emitting light may be changed, light emitting efficiency may be reduced, driving voltages may be increased, and lifetime may be shortened. In order to prevent those problems, a glass transition temperature (Tg) of hole injecting materials, hole transporting materials and emitting materials. In order to have high Tg, molecules of the materials have many aromatic groups which cause crystallization of the molecules 11 during the formation of a thin film and the crystallization may cause defects in the thin film. Meanwhile, the high Tg increases sumlimation temperature and the lifetime of organic light emitting devices may be decreased due to decomposition of materials during deposition or ununiform deposition.
Japanese Patent Publication No. hei 5-234681 discloses N,N-diphenyl-N,N-di(1-naphtyl)-1,1-biphenyl-4,4-diamine (NPD) having a higher Tg than N,N-diphenyl-N,N-dimethylphenyl-1,1-biphenyl-4,4-diamine (TPD) which has been commonly used in the art as a hole transporting material to improve thermal stability by introducing a condensed aromatic ring into a molecule.